swap rates

can a broker change swap rates everyday?....forex.com for my account is doing it for the past month or so and always changing them to pay me the lowest interest and charging me the highest interest on my open positions

thank you for your responses
goran

from my knowledge those rates are based on overnight lending rates between banks, so in theory they would vary daily...but let's wait for someone else to confirm this, i'm not completely positive i'm correct.